Clinical trials for MED found minimal side effects. ED can sometimes signal an underlying medical problem, like heart disease or diabetes , that needs to be treated separately. Best for. However, Viagra Connect is only available over the counter in the licensed strength of 50mg. Medicines that block an enzyme called CYP3A4.Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its . According to price-comparison site , generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with . Oral medications, like Viagra and Cialis, which require a prescription and are commonly used to treat ED, can take 30 minutes to take effect, she adds. Injections take less time .